CDL Endorsements Explained
Endorsements expand what you're allowed to drive on a CDL. Each one has its own knowledge test (and Hazmat requires a TSA security check). Pick an endorsement to read a study guide and get a list of every state-specific practice test we offer for it.
General Knowledge GK
The foundation test taken by every CDL applicant in every state.
Air Brakes L (restriction removed)
Required if your test vehicle has air brakes — otherwise an L-restriction is added.
Combination Vehicles GK (Class A)
Required for Class A: tractor-trailer driving, coupling, off-tracking and trailer brakes.
Hazardous Materials H
Required to haul placarded amounts of hazardous materials. Includes a TSA background check.
Passenger P
Required to drive a vehicle designed to carry 16+ passengers (including the driver).
School Bus S
Required to drive a school bus carrying students. Adds federal student-safety rules on top of P.
Tank Vehicle N
Required to haul liquids or gases in a tank rated 1,000+ gallons aggregate.
Doubles / Triples T
Required to pull more than one trailer behind a single tractor.
How CDL endorsements work
A CDL endorsement is a federally recognized addition to your Commercial Driver's License that authorizes you to operate a specific kind of commercial vehicle or carry a specific kind of cargo. Some endorsements — like Air Brakes (technically a removed restriction rather than an added endorsement) and General Knowledge — are required for almost every CDL holder. Others, like Hazmat or School Bus, are added only when your job requires them.
Each endorsement is granted by passing a written knowledge test administered by your state's licensing agency. The Hazmat endorsement is the only one that also requires a separate federal background check (the TSA Hazardous Materials Endorsement Threat Assessment) including fingerprinting. The Passenger and School Bus endorsements additionally require a behind-the-wheel skills test in a vehicle representative of the class you'll be driving.
You don't have to add every endorsement at once. Most drivers start with the endorsements their first job requires, then add more later as their career evolves. Every endorsement adds either a small fee or a renewal cycle, so it's worth being deliberate about which ones you actually need.